Heart Rate Variability (HRV) quantifies the fluctuations of the lengths of consecutive heart beat intervals. HRV reflects the regularity of heart beats, with higher regularity implying lower HRV, and is a reliable descriptor of many physiological factors modulating the normal rhythm of the heart. HRV is a crucial diagnostic tool and provides a powerful means of observing the interplay between the sympathetic and parasympathetic nervous systems and is thought to reflect the heart's ability to adapt to changing circumstances by detecting and quickly responding to unpredictable stimuli. As such, HRV metrics are useful in characterizing physiological stress.
Presently, Holter monitors or other portable devices for are used to continuously monitoring various electrical activity of the cardiovascular system for at least 24 hours (often for two weeks at a time). Recent studies have indicated that the duration of time that a patient is monitored may improve the accuracy of the results.
For example, one recent study illustrated the need for long-term monitoring in detecting of recurrences after ablation for atrial fibrillation (“AF”). See N. Dagres, et. al., “Influence of the duration of holter monitoring on the detection of arrhythmia recurrences after catheter ablation of atrial fibrillation: Implications for patient follow-up,” International Journal of Cardiology, vol. 139, no. 3, pp. 305-306, 2010. As is described in Dagres, a 24-hour Holter detected 59% of patients with those recurrences, a 48-hour Holter detected 67%, a 72-hour Holter detected 80%, and a 4-day recording detected 91% of the recurrences that were detected with a complete 7-day recording. Consequently, the study concluded that a Holter duration of less than 4 days misses a great portion of recurrences.
As the need to monitor patients for longer periods of times has developed, there has been a corresponding need for monitoring devices which are smaller, more power efficient, available on a variety of mobile platforms and with new lower RF protocols. This has led to the development of wearable ECG monitoring devices that are capable of continuously recording and transmitting ECG signals for 7-14 days or longer periods of time. In addition to the improved ability to track and transmit these signals, however, there is a need for improvements in analyzing the data so as to accurately and efficiently measure HRV.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced.